Interplay of Thermalization and Strong Disorder: Wave Turbulence Theory, Numerical Simulations, and Experiments in Multimode Optical Fibers

Rayleigh-Jeans prethermalization and wave condensation in a nonlinear disordered Floquet system

“…During the refereeing process of this manuscript, we became aware of the work [119] which finds similar results with nonlinear optics experiments realized in multimode optical fibers with an effectively time-dependent (although not periodically) random potential. In particular, a regime with RJ thermalization or wave-condensation is observed before the systems boils to a featureless uniform state.…”

Spectral-temporal-spatial customization via modulating multimodal nonlinear pulse propagation

“…For example, the application of MMFs to fiber lasers could permit the development of low-cost light sources with dramatically higher pulse energy and average power due to the larger mode areas of the MMFs 13 – 16 . More importantly, the rich spatiotemporal dynamics and complex intermodal interactions in MMFs constitute a broad avenue for controlling nonlinear wave propagation, opening up possibilities for intriguing physics and applications such as spatiotemporal light control 17 , 18 , nonlinear frequency generation 4 , 12 , 19 – 21 , nonlinear optical imaging and sensing 22 – 25 , optical wave turbulence 26 – 29 , and optical computing 30 , 31 .…”

“…Here we introduce a simple but effective way of controlling multimodal nonlinear effects in high-power regimes by exploiting not only the spatial but also the temporal degrees of freedom. Complementary to manipulating the input pulses that seed the nonlinear pulse propagation, we propose to modulate the multimodal nonlinear pulse propagation processes by introducing programmable time-dependent disorders along the fiber 26 , which is implemented as axial-position-dependent macro-bending. This was made possible by using a single 3D-printed modulating device dubbed fiber shaper (conceptually depicted in Fig.…”

Observation of light thermalization to negative temperature Rayleigh-Jeans equilibrium states in multimode optical fibers

“…RJ thermalization to usual positive temperature equilibriums has been recently demonstrated experimentally in MMFs [23][24][25][26], on the basis of a spatial beam-cleaning effect [27][28][29][30][31]. As described by the wave turbulence theory [32][33][34][35][36] applied to MMFs [37][38][39][40], the thermalization to a positive temperature equilibrium is characterized by a transfer of power (particle number) toward the low-order modes of the MMF. In marked contrast, here we report the observation of thermalization to a NT equilibrium featured by a power transfer to high-order modes (direct flow of particles), as well as a transfer of energy to loworder modes (inverse flow of energy).…”

“…Negative temperatures.-The irreversible process of RJ thermalization is described by the wave turbulence theory [32][33][34][35][36], which provides a nonequilibrium description of light propagation in MMFs [37][38][39][40]. An equilibrium thermodynamic formulation of multimode optical systems has been recently developed [17,47].…”